Sudden infant death syndrome (SIDS) may be attributed to disturbance in the regulation of brain chemical serotonin, said researchers of the European Molecular Biology Laboratory in Monterotondo, Italy.

Serotonin is an neurotransmitter that transmits signals between brain cells. It is mostly associated with moods.

Published in the July 4 issue of Science, the research suggests that any alterations in normal serotonin level may generate changes in heart rate and body temperature, as were produced in mice during the study.

"This mouse model is important. Causing dysfunction in brainstem serotonin can lead to death in a majority of affected animals," Marian Willinger, a SIDS expert with the U.S. National Institute of Child Health and Human Development, said at a press conference Thursday.

The severe cardiac and thermal variations that occurred in the mice are parallel to risk factors associated with SIDS.

Sweltering babies by over-bundling them is a known risk factor for SIDS as is stomach sleeping, which causes higher heart rate alterations than back sleeping.

About 2,500 infants die suddenly each year, in the U.S. alone. It is the third leading cause of death among infants aged between a week and a year.

Exact causes of the SIDS have not been identified yet. Some previous studies have connected bacterial infections from Staphylococcus aureus and Escherichia coli to the cot deaths. Another study, last year revealed that mothers who smoked during their pregnancy also posed a high risk of SIDS to their babies.

The recent research was not intended to develop a mouse model of SIDS but researchers were aiming to study the serotonin system and how the body maintains its levels.

"At first sight the mice were normal. But then they suffered sporadic and unpredictable drops in heart rate and body temperature. More than half of the mice eventually died of these crises during a restricted period of early life. It was at that point that we thought it might have something to do with SIDS," says Cornelius Gross, one of the researchers.

The scientists noticed that it is not the complete block but a dysfunction in serotonin secretion which causes the death.

The findings could help discover new ways to identify the babies, who are at the greatest risk of SIDS, said Gross. Similar findings were reported in a study, two years ago.

However, the scientists said they don't anticipate a pharmacological intervention to prevent SIDS.

"Drug therapy is probably not the way to do this. These neurotransmitters control a huge number of functions," said Willinger.